Pass function from Scala.js to Javascript function?

Question

I've defined function in Scala.js like this:

val myFunction: js.Function1[js.Array[String], Boolean] = (data: js.Array[String]) => true

And also defined Javascript function on the page:

function callFunction(inputFunction){
  console.log(inputFunction(["10"]))
}

When I make a call from Scala.js:

GlobalScope.callFunction(myFunction)

I got error:

Uncaught TypeError: inputFunction is not a function

What I'm doing wrong and how to fix it?

Definition of the GlobalScope:

@JSGlobalScope
@js.native
object GlobalScope extends js.Any {
  def GlobalScope.callFunction(someFunction: (js.Array[String]) => Boolean): Unit = js.native
}

What is the definition of GlobalScope and its method callFunction? — sjrd
– sjrd, Commented Jul 14, 2018 at 9:33

sjrd · Accepted Answer · 2018-07-14 13:18:06Z

1

The definition of callFunction in GlobalScope is erroneous. It asks for a js.Array[String] => Boolean, which is a Scala function from js.Array[String] to Boolean, not a JavaScript function. When you call it, even if you give it a js.Function1[js.Array[String], Boolean] (which is correct), the Scala type system will insert an implicit conversion from js.Function1 to scala.Function1 to conform to the expected type. But then of course the JavaScript code in callFunction receives a Scala function and is not happy with it.

The solution is to fix the definition of callFunction to take a js.Function1:

@JSGlobalScope
@js.native
object GlobalScope extends js.Any {
  def callFunction(someFunction: js.Function1[js.Array[String], Boolean]): Unit = js.native
}

answered Jul 14, 2018 at 13:18

sjrd

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